function checkEmail(emailStr) {
               if (emailStr.length == 0) {
		   alert('Please enter a valid email address.');
                   return false;
               }
               var emailPat=/^(.+)@(.+)$/;
               var specialChars="\\(\\)<>@,;:\\\\\\\"\\.\\[\\]";
               var validChars="\[^\\s" + specialChars + "\]";
               var quotedUser="(\"[^\"]*\")";
               var ipDomainPat=/^(\d{1,3})[.](\d{1,3})[.](\d{1,3})[.](\d{1,3})$/;
               var atom=validChars + '+';
               var word="(" + atom + "|" + quotedUser + ")";
               var userPat=new RegExp("^" + word + "(\\." + word + ")*$");
               var domainPat=new RegExp("^" + atom + "(\\." + atom + ")*$");
               var matchArray=emailStr.match(emailPat);
               if (matchArray == null) {
		   alert('The email address provided is not a valid email address.\nPlease enter a valid email address.');
                   return false;
               }
               var user=matchArray[1];
               var domain=matchArray[2];
               if (user.match(userPat) == null) {
		   alert('The email address provided is not a valid email address.\nPlease enter a valid email address.');
                   return false;
               }
               var IPArray = domain.match(ipDomainPat);
               if (IPArray != null) {
                   for (var i = 1; i <= 4; i++) {
                      if (IPArray[i] > 255) {
		         alert('The email address provided is not a valid email address.\nPlease enter a valid email address.');
                         return false;
                      }
                   }
                   return true;
               }
               var domainArray=domain.match(domainPat);
               if (domainArray == null) {
		   alert('The email address provided is not a valid email address.\nPlease enter a valid email address.');
                   return false;
               }
               var atomPat=new RegExp(atom,"g");
               var domArr=domain.match(atomPat);
               var len=domArr.length;
               if ((domArr[domArr.length-1].length < 2) ||
                   (domArr[domArr.length-1].length > 3)) {
		   alert('The email address provided is not a valid email address.\nPlease enter a valid email address.');
                   return false;
               }
               if (len < 2) {
		   alert('The email address provided is not a valid email address.\nPlease enter a valid email address.');
                   return false;
               }
               return true;
            }